The invention relates generally to a primer composition and, in particular, to a colorless primer composition that can be used to provide a permanent, detectable primer to be used in the construction industry for identifying proper conditioning of a plastic pipe, which will not cause visible stain.
Purple primer is a well-known product used in the plumbing and construction industry. It is used to properly condition a plastic pipe, such as PVC (polyvinyl chloride) or CPVC (chlorinated PVC), prior to jointing two separate pipes by a cemented joint.
According to American Society for Testing and Materials (“ASTM”) standards D2564, D2235, D3138 and F493, PVC or CPVC plastic pipes must be cleaned and conditioned prior to joining them with a plastic pipe cement bond. Purple primer plays an important role in this process, in that it softens or tackifies the surface of the plastic pipe, allowing a more effective fusing of the two pipes through the formation of the cement bond. The ASTM standards call for the use of a solvent primer, which can effectively remove surface dirt grease and grime and soften the surface of a plastic pipe in order that the application of a plastic pipe cement will form a permanent, air tight and water tight bond. Traditional primer typically includes solvents, such as tetrahydrofuran, methyl ethyl ketone, acetone, cyclohexanone of N-methyl pyrrilidone, in which PVC or CPVC resin is dissolved along with fillers, stabilizers and colorants.
Traditional primers are based on clear, colorless solvents such as acetone or methyl ethyl ketone (MEK) and a colored, permanent dye, typically purple in color. The colored dye has no functional purpose other than coloring the pipes to allow an inspector to visually confirm that a primer has been applied before applying cement. Standards within the industry, such as the Uniform Plumbing Code (UPC) and the International Plumbing Code (IPC), require the use of a permanent, purple colored primer in the process of producing a permanent pipe cemented bond. Because inspection at a construction site may occur on a day or time other than when the actually cementing is taking place, the inspector depends on the presence of the purple color on the pipe joints as evidence that a primer has been properly applied.
Traditional purple primers allow for quick visual inspections. The permanent color dye in the primer cannot be removed by cleaning with water or other solvent systems. The coloring cannot be removed by abrading with sand paper or other abrasive medium without severely scarring the applied surfaces. While the permanency of the purple color is necessary, it can also be a troublesome characteristic of traditional purple primers.
Because of the permanent characteristic of the dye, traditional purple primers immediately leave a permanent, purple stain on any porous or plastic surface, such as countertops, vinyl floors, and/or carpets, upon contact. The stain cannot be removed through any normal cleaning method, without destroying the stained surface. This has been a serious problem in construction, home repair or other processes, because the primer often comes in contact with porous or plastic surfaces through unintentional applications or accidental spills, leaving plastic or porous surfaces with an unsightly stain. While stains on pipes can be hidden behind finished walls, other stained surfaces often have to be replaced totally.
Because of this permanent consequence, there is a need for stainless, yet permanent, detectable purple primer.
Accordingly, it is desirable to provide an improved stain free purple primer that overcomes drawbacks and inadequacies of the prior art.